Hybridization and Dehybridization of Plasmonic Modes

TL;DR

This study investigates how substrate-induced hybridization of plasmonic modes in silver nanocylinders affects their spectral and near-field properties, revealing implications for sensing applications and mode stability.

Contribution

It provides experimental and numerical analysis of mode hybridization and dehybridization in plasmonic nanoparticles influenced by the environment and substrate effects.

Findings

Hybridization depends on substrate reflection and incident light superposition.

Deposition of a polymer layer causes hybridized modes to vanish.

Mode behavior can change unexpectedly in sensing environments.

Abstract

The plasmon resonances (modes) of a metal nanostructure can be defined as a dipole, a quadrupole, or high-order modes depending on the surface charge distribution induced by the incident field. In a non-symmetrical environment or clusters, the modes can hybridize and exhibit different behavior and properties. In this work, we study experimentally and numerically the substrate-induced hybridization of plasmonic modes of a silver nanocylinder. The applications of plasmonic nanoparticles such as refractive index sensing and enhanced spectroscopies often rely on the sustained mode spectral position and specific spatial near-field distribution. However, we show that the implementation of such plasmonic nanoparticles in a sensing system can result in a change of the modes nature, its hybridization or dehybridization. These changes are not clearly pronounced in the far-field spectra and then may result in unexpected modifications of the sensor behavior. We show that the hybridization between the dipolar and quadrupolar modes of the plasmonic nanoparticle on the substrate results from quadrupolar mode excitation due to the superposition of the reflected and incoming light and, then, depends on the reflection of the substrate. The existence of the hybridized modes strongly depends on the surrounding environment of nanoparticles, and after the deposition of the nanometric polymer layer on top of the nanoparticle the hybridized modes vanish and are replaced by uncoupled multipolar resonances.